How do scripts such as vBulletin launch regular maintenance jobs without using cron jobs?

Question

How do scripts such as vBulletin launch regular maintenance jobs without cron jobs? For example, vBulletin does not update thread view counts in real-time, and only does so hourly according to their documentation. However, they don't use cron jobs to do that, so how do they do it?

I ask because I would like to do something similar on one of my sites, but don't know how they do this magic?

Answer 1

@Mitzimoto is correct. https://www.vbulletin.com/docs/html/scheduled_tasks_intro

vBulletin’s scheduled tasks system does not constantly run on the server like cron and scheduled tasks in Windows®. Tasks are automatically run when a user browses your board, so if your board does not have any traffic at a given time, tasks scheduled to run then will not run until later. vBulletin’s scheduled tasks also will not run when you board is turned off.

Answer 2

I believe they use page loads and timestamps. In other words, every time your forum receives a page view, it checks the current time against the time of the next scheduled job. If the current time is >= the scheduled time, the job will run.

Of course, the downside to this is that if your forum doesn't get a lot of page views you can't guarantee a job will run at a specific time. The accuracy is directly related to the activity on your forum.